DIY Webcam Diffraction Grating Spectrometer

In this post we propose the construction of a diffraction grating spectrometer based on webcam and software Theremino Spectrometer. The spectrometer is a fundamental tool that allows measurement of the spectrum of a light source, ie the properties of light as a function of its wavelength. The spectrometer that we propose uses the principle of interference in a diffraction grating in order to decompose the light radiation in its wavelengths and subsequently measuring its intensity with a high-resolution webcam.

Diffraction Grating

A monochromatic light beam that is incident on a grating gives rise to a transmitted beam and various diffracted beams, at angles that depend on the ratio between the distance between the lines of the grating and the wavelength of the light. So, if the light beam is composed of multiple wavelengths, the decomposition of the beam into its components is obtained.

The light with a longer wavelength is deflected to a larger angle with respect to the incident direction (angle of diffraction ) . For each wavelength more rows can be observed. The number of rows that are counted from the middle line, which is not skewed with respect to the incident beam and is taken as a reference , it is said “order” and is often denoted by the letter m.

Light Beam Diffracted by a GratingLamp Spectrum obtained from a Diffraction Grating